Crows Go to the Head of the Class

Bright Betty. A crow uses a wire hook she made to fish food from a tube. CREDIT: A. WEIR ET AL., SCIENCE 297, 981 (2002)

Tools were thought to be the hallmark of humanity, until observations of wild primates uncovered widespread tool use. But cognitive studies suggest primates use tools mainly by trial and error, whereas humans understand the principles at work--such as gravity and force--and exploit them to make novel tools. Birds, although they often have relatively large brains, are commonly thought to carry out tasks by rote. But in 1996, researchers reported that New Caledonian crows, named for their South Pacific island home, snip twigs with their beaks to make hooked tools (for more, see ScienceNOW, 9 March 2000). The study offered tantalizing evidence that a supposedly human ability had evolved in another animal.

While experimenting on New Caledonian crows, ecologist Alex Kacelnik and colleagues at the University of Oxford observed a female named Betty bend a straight wire into a hook to retrieve a food reward (see a movie, 1.3 megabytes). When the researchers gave Betty a straight wire in subsequent experiments, she repeated the trick in nine of 17 trials, they report in the 9 August issue of Science. She had no prior experience with wire, so the ability to make such a tool suggests that she was able to understand the properties of a new material and how to modify it--a feat never observed in any creature but humans. Kacelnik says that Betty's toolmaking is too complex to have happened by chance.

The study shows that "crows' natural abilities may indeed be based on sophisticated cognitive skills," says ecologist Gavin Hunt of the University of Auckland, New Zealand, who discovered twig use in New Caledonian crows. Kacelnik adds that flexible thinking is not a uniquely human trait, but an evolved response to the crows' needs. "Understanding the evolution of cognition will require paying attention to the social ecology of each species, rather than using the human yardstick."

Kacelnik plans to test other individuals to uncover how general an understanding the crows have for new material and their potential uses, and whether this understanding is different from humans'. Hunt would like to see crows make other new tools before he's convinced of their knack for problem solving.

--BEN SHOUSE

Related sites
Kacelnik's crow page
Hunt's home page